html {
  font-family: sans-serif;
}

body {
  margin: 0;
}

header {
  background: purple;
  height: 100px;
}

h1 {
  text-align: center;
  color: white;
  line-height: 100px;
  margin: 0;
}

article {
  padding: 10px;
  margin: 10px;
  background: aqua;
}

/* Add your flexbox CSS below here */

section {
  display: flex;
}

article {
  flex: 1 200px;
}

article:nth-of-type(3) {
  flex: 3 200px;
  display: flex;
  flex-flow: column;
}

article:nth-of-type(3) div:first-child {
  flex: 1 100px;
  display: flex;
  flex-flow: row wrap;
  align-items: center;
  justify-content: space-around;
}

button {
  flex: 1 auto;
  margin: 5px;
  font-size: 18px;
  line-height: 1.5;
}